1. Field of the Invention
The present invention relates to a projected beam-type smoke detector having a light emitter and a light receiver for smoke detection in separate units, and in particular to a projected beam-type smoke detector which allows any of adjustment modes to be automatically set in each section of the light emitter and the light receiver in the adjustment of optical axis and light input level and outputs an irregularity signal when an irregularity occurred.
2. Description of the Related Art
In a prior art projected beam-type smoke detector, the adjustment of an optical axis is performed by looking into the collimation aperture of a light receiver from behind it to see a light emitter and by looking into the collimation aperture of the light emitter from behind it to see the light receiver. Light input is then adjusted referring to the output of a monitor. Sensitivity setting is performed by setting the range selection switch according to a monitoring range in use.
For example, U.S. Pat. No. 4,651,013 discloses the smoke detector shown in FIG. 19. In this smoke detector, adjustment of optical axis and setting of sensitivity are performed as follows. To adjust the optical axis, an optical axis fixing screw 102 on a light emitter is loosened. The main unit of the emitter is adjusted while looking into a collimation aperture 101 until the center of the aperture 101 is aligned with the center of the collimation aperture 101 of the light receiver 100. The fixing screw 102 is lightly tightened to the degree that the main unit is still movable.
In the same manner, the light receiver 100 is adjusted so that it is aligned with the center of the collimation aperture 101 of the light emitter, and then the fixing screw 102 is lightly tightened.
Monitor output (light input level) is then adjusted. The monitor cover 103 of the light receiver 100 is opened to check that the monitor lamp in a set switch 104 flashes.
Next, a range selection switch 105 is set to a position of "adjustment".
A monitor plug 107 supplied is plugged into a monitor jack 106 to connect a measuring mean, for example, a multimeter 108.
Two output adjusting potentiometers 109 (for coarse adjustment), 110 (for fine adjustment) are turned until the multimeter 108 reads an appropriate monitor output.
Each of the light emitter and the light receiver 100 is moved gradually one at a time to find the positional setting that gives the maximum monitor output, and the optical axis fixing screw 102 on each of the light emitter and the light receiver 100 is tightened there.
When the optical axis adjustment and the optical axis fixing of the light receiver 100 and the light emitter is performed, two output adjusting potentiometers 109, 110 are turned until an appropriate monitor output, again.
Active monitoring state is set by setting the range selection switch 105 to the sensitivity setting corresponding to the monitoring range (the range from the light emitter to the light receiver 100) in use and by operating the setting switch 104.
Adjustment of the optical axis and light input level has thus involved a series of adjustment steps as above.
In the course of adjustment in the conventional projected beam-type smoke detector, a measuring instrument should be connected to the smoke detector main unit that is typically mounted at a high position. The smoke detector is then adjusted while observing the measuring instrument there. Thus, the adjustment is difficult and risky. Furthermore, the adjustment cannot be performed without measuring instrument.
Furthermore, the projected beam-type smoke detector is typically installed onto a wall surface. Accordingly, a need exists for a smoke detector which allows optical axis adjustment and sensitivity setting to be performed from sides or from front.
In light of the need, some smoke detectors are equipped with a lamp indicative of light input level to allow optical axis adjustment and setting to be performed in the state that a front cover took off.
For example, FIGS. 20 and 21 show such a conventional projected beam-type smoke detector. A front cover 120 is first removed. The plug for spare battery for the control panel is connected to a power input connector 121. Next, disposed on one side of the main unit 122 is a mode switch 123 having switch positions for optical axis, light input level and monitor setting. The mode switch 123 is set to a position of "optical axis". The optical axis adjustment is performed by turning adjusting screws 124. When the mode switch 123 is set to a position of "optical axis", around of a lens 128 is flashed by flash of a optical axis indicator means set up inside of the lens 128. Therefore, the optical axis adjustment is to be easily. After the optical axis adjustment, a range setting switch 125 is set according to the monitoring range in use. With the mode switch 123 set to "light input level", a light input level control 126 is turned.
Three light-input level indicator lamps 127 are provided, one indicative of insufficient light input level range, another indicative of optimum light input level range, and the third indicative of excess light input level range. The light input level control 126 is turned until the optimum level lamp flashes. When the insufficient level lamp flashes, the light input level control 126 is turned in the direction of light input level increase. When the excess level lamp flashes, the light input level control 126 is turned in the direction of light input level drop. The light input level control 126 is thus turned for the optimum light input level observing three light input level lamps 127.
In succession to the optical axis and light input level adjustments, the mode switch 123 is set to a position of "monitor", the battery is disconnected, and the front cover 120 is mounted.
Initial setting is performed by pressing the set button 129 from the front of the light emitter for a predetermined time. Light pickup output in the absence of smoke is then stored as its initial value. A fire determination level is computed on the basis of the stored initial value and the setting of the range selection switch that sets sensitivity according to the monitoring range (the range between the light emitter and the light receiver). The monitoring function is thus activated.
In the above conventional projected beam-type smoke detector, a fire signal or an irregularity signal may be generated when an operator inadvertently block the optical path by his hand in the course of optical axis and light input level adjustments. With the adjustment mode selected by switching operation, the fire signal and the irregularity signal are prevented from being sent to the control panel.
Both Japanese Patent Application Laid-Open No. 175999/1994 and Japanese Utility Model Application Laid-open No. 82789/1994 have disclosed such a projected beam-type smoke detector wherein each of the light emitter and the light receiver has on its front an operation block that is adjusted with its front cover removed.
In the adjustment of the conventional projected beam-type smoke detector, with the mode switch set to a position of "optical axis", the optical adjustment is performed. In succession, with the mode switch set to a position of "light input level", light input level adjustment is performed. Then, with the mode switch is set to a position of "monitor". Switching operation is complex, and a poor adjustment efficiency thus results.
To disable the fire signal and the irregularity signal, switching to the adjustment mode is required. If the front of the light receiver is inadvertently covered by hand prior to switching to the adjustment mode, the fire signal or the irregularity signal may be accidentally generated.
To flash the light input level lamps, the mode switch should be set to a position of "light input level". To extinguish the lamps, the mode switch should be set a position of "monitor", when the optical axis adjustment and light input level adjustment are complete. Switching on or Off the lamps needs a plurality of switching steps. Thus, the adjustment of the smoke detector is complex and a poor instrument operability results.
Furthermore, to flash an optical axis lamp, the mode switch should be turned to a position of "optical axis". To extinguish the optical axis lamp, the mode switch should be set to one of the other positions. The adjustment is accordingly complex and its efficiency is poor.
In the course of the adjustment of optical axis and light input level, the cover may be mounted with sensitivity setting unadjusted by the range setting switch, or sensitivity setting may be performed with the cover left unmounted. Then, power may be possibly connected with no corrective action taken, Since there is no function available to alarm the operator in such cases, the incorrect step goes undetected. Namely, with the smoke detector in its monitor state in succession to the adjustment, the operator fails to recognize the fact that the smoke detector remains incapable of monitoring smoke in a normally operational manner.
To store the initial value, the set button should be pressed after the cover is mounted. This may be an additional step that occasionally escapes attention of the operator. Furthermore, in the event of power interruption, the stored value will be lost, and the button pressing must be repeated.
Some projected beam-type smoke detectors are provided with a light emitter and a light receiver that faces the light emitter with both units spaced apart by a predetermined range therebetween. At regular intervals, light is emitted in a pulse and attenuation of the pulsed light by smoke is then detected. In such a smoke detector, monitoring intervals (flashing intervals of pulse light) are set to a constant, 3 seconds, for example. Therefore, time delay takes place before an adjustment of optical axis, for example, is reflected as a change in signal. This presents difficulty in adjustment.
To resolve these problems, the smoke detector disclosed in the already cited U.S. Pat. No. 4,651,013 allows monitoring interval to be shortened by connecting a measuring instrument to the monitor terminal of a light receiver.
Specifically, by providing the monitor terminal that gives at the monitoring interval a monitor signal in response to the output of reception of pulsed light and by providing means for shortening the monitor interval in a monitor state with the measuring means connected to the monitoring terminal, to reduce delay time in the monitor signal output, and to be adjustment easily.
Even if the monitoring interval is switched in this way, however, the measuring instrument should be connected to the monitor terminal. The adjustment is still equally complex and thus a poor operability in adjustment results.